1. Field of the Invention
The present invention relates to a laser light intensity controller for an optical apparatus.
2. Description of the Related Background Art
An optical pickup apparatus, which is used for reading information from an optical disc or writing information into an optical disc, is provided with a laser light intensity controller which monitors a portion of a laser beam emitted from a light source to irradiate the disc with the laser beam with an appropriate light intensity.
In the laser light intensity controller, for preventing a decrease in the light intensity of a laser beam irradiated to a disc caused by the rotation of a polarization plane of the laser beam, due to a change in temperature which affects optical parts such as a light source, a portion of the laser beam emitted from the light source, if the laser beam irradiated to the disc is the P-polarization component, is separated by a polarizing beam splitter. The separated laser beam is further separated by another polarizing beam splitter, and received by a front monitor which serves as a light receiving means, to drive the light source in response to an output signal of the front monitor.
However, the conventional laser light intensity controller has a problem in that many optical parts are required, so that its optical system is complicated. In the case of rotating the polarization plane of the laser beam, if the laser beam to be irradiated onto the disc is a P-polarization component, not only the P-polarization component but also a slight amount of the S-polarization component reaches the optical disc. The S-polarization component becomes noise, and the noise makes the read and write operations unstable.
An object of the present invention is to provide a laser light intensity controller which can stably control the optical intensity of a laser beam emitted from a light source in an optical pickup apparatus with a simple configuration, even if the plane of polarization of the laser beam rotates, and which can stably perform read and write operations for a recording medium.
According to the present invention, there is provided a laser light intensity controller for controlling a light intensity of a laser beam emitted from a light source of an optical apparatus, comprising: a polarization separating device for passing therethrough most of one of an x-direction polarization component perpendicular to a direction in which a laser beam emitted from the light source travels and a y-direction polarization component parallel with the traveling direction and for reflecting a little portion of the one polarization component as monitoring light; a light receiving device for receiving the monitoring light reflected by the polarization separating device to generate a light intensity signal indicative of the received light intensity; a driving device for driving the light source in accordance with the light intensity signal; and an optical element arranged between the light source and the polarization separating device for passing only the one polarization component.